Using DCPIP and DPC in PSII activity assays--Help.

Has anyone out there used DCPIP and DPC to do PSII activity assays? I'm
trying to do this with algal thylakoids and just can't get the system to
work. I'm following the information in Vernon and Shaw's papers, but I seem
to be getting a reaction between DCPIP and DPC alone without thylakoids as
well as an interaction with oxygen, which does not seem to have been
reported. Any information? Beatrice Grabowski.